function [ u ] = splitStep1h( u , dimR, h ,w,  alpha, b2 , gamma, k,dr)
        for rr=2:dimR-1
            line = u(rr,:);
            spectrum = (fft(line));
            spectrum=spectrum.*exp( 1i*b2/2*w.^2*(h) );%- 1i*gamma*w.*abs(spectrum).^2*h) ; 
            
            f=ifft(spectrum);
            f=f.*exp(-alpha*h/2 + 1i*gamma*((abs(f)).^2)*h );
            
            f=f.*exp(-1i*h/4/k* (u(rr-1,:) - 2* u(rr,:) + u(rr+1,:)/dr/dr) ); % beam propagation
            
                            
            
            u(rr,:)=f;
            

        end

end

